Nestor, this is the solution to the problem:
Step 1: Let's isolate x in the first equation, this way:
2x + 3y = -15
2x = -15 - 3y
Dividing by 2 at both sides:
2x/2 = (-15 - 3y)/2
x = (-15 - 3y)/2
Step 2: Let's substitute x and solve for y in the second equation, as follows:
-7x - 4y = -6
-7 (-15 - 3y)/2 - 4y = -6
Solving parenthesis:
105 +21y/2 - 4y = -6
Multiplying by 2 at both sides:
105 + 21y - 8y = -12
Like terms:
13y = -12 - 105
13y = -117
y = -9
Step 3: Let's solve for x in the first equation, this way:
2x + 3y = -15
2x + 3 * -9 = -15
2x -27 = -15
Adding 27 at both sides:
2x - 27 + 27 = -15 + 27
2x = 12
Dividing by 2 at both sides:
2x/2 = 12/2
x = 6